121 lines
3.1 KiB
Rust
121 lines
3.1 KiB
Rust
use crate::core::Size;
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use crate::geometry::{self, Frame};
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use crate::Cached;
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use std::cell::RefCell;
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/// A simple cache that stores generated geometry to avoid recomputation.
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///
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/// A [`Cache`] will not redraw its geometry unless the dimensions of its layer
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/// change or it is explicitly cleared.
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pub struct Cache<Renderer>
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where
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Renderer: geometry::Renderer,
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{
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state: RefCell<State<Renderer::Geometry>>,
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}
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impl<Renderer> Cache<Renderer>
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where
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Renderer: geometry::Renderer,
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{
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/// Creates a new empty [`Cache`].
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pub fn new() -> Self {
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Cache {
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state: RefCell::new(State::Empty { previous: None }),
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}
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}
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/// Clears the [`Cache`], forcing a redraw the next time it is used.
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pub fn clear(&self) {
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use std::ops::Deref;
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let previous = match self.state.borrow().deref() {
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State::Empty { previous } => previous.clone(),
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State::Filled { geometry, .. } => Some(geometry.clone()),
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};
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*self.state.borrow_mut() = State::Empty { previous };
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}
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/// Draws geometry using the provided closure and stores it in the
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/// [`Cache`].
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///
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/// The closure will only be called when
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/// - the bounds have changed since the previous draw call.
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/// - the [`Cache`] is empty or has been explicitly cleared.
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///
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/// Otherwise, the previously stored geometry will be returned. The
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/// [`Cache`] is not cleared in this case. In other words, it will keep
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/// returning the stored geometry if needed.
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pub fn draw(
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&self,
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renderer: &Renderer,
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bounds: Size,
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draw_fn: impl FnOnce(&mut Frame<Renderer>),
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) -> Renderer::Geometry {
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use std::ops::Deref;
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let previous = match self.state.borrow().deref() {
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State::Empty { previous } => previous.clone(),
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State::Filled {
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bounds: cached_bounds,
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geometry,
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} => {
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if *cached_bounds == bounds {
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return Cached::load(geometry);
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}
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Some(geometry.clone())
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}
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};
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let mut frame = Frame::new(renderer, bounds);
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draw_fn(&mut frame);
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let geometry = frame.into_geometry().cache(previous);
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let result = Cached::load(&geometry);
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*self.state.borrow_mut() = State::Filled { bounds, geometry };
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result
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}
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}
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impl<Renderer> std::fmt::Debug for Cache<Renderer>
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where
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Renderer: geometry::Renderer,
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{
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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let state = self.state.borrow();
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match *state {
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State::Empty { .. } => write!(f, "Cache::Empty"),
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State::Filled { bounds, .. } => {
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write!(f, "Cache::Filled {{ bounds: {bounds:?} }}")
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}
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}
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}
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}
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impl<Renderer> Default for Cache<Renderer>
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where
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Renderer: geometry::Renderer,
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{
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fn default() -> Self {
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Self::new()
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}
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}
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enum State<Geometry>
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where
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Geometry: Cached,
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{
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Empty {
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previous: Option<Geometry::Cache>,
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},
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Filled {
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bounds: Size,
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geometry: Geometry::Cache,
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},
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}
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